Apparatus for controlling the temperature of a wafer located...

Drying and gas or vapor contact with solids – Apparatus – Houses – kilns – and containers

Reexamination Certificate

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C034S566000, C414S936000

Reexamination Certificate

active

06370793

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for manufacturing semiconductor devices. More particularly, the present invention relates to a wafer pre-alignment stage and to apparatus for controlling the temperature of a wafer held by a wafer chuck of the pre-alignment stage.
2. Description of the Related Art
Generally, semiconductor devices such as semiconductor chips are manufactured by subjecting a wafer made of silicon to a series of semiconductor manufacturing processes such as lithography, light exposure, ion implantation, chemical and mechanical polishing, chemical and physical vapor deposition, and plasma etching or the like.
The light exposure process typically comprises wafer alignment and UV-light exposure steps. More specifically, a wafer coated with photoresist is positioned on a wafer stage in proper alignament with a mask, and then the wafer is exposed to UV-light to form a photoresist pattern.
Such a light exposure process and attendent apparatus are disclosed in U.S. Pat. No. 5,706,076 (issued to Minoru Takeda on Jan. 6, 1998), U.S. Pat. No. 5,781,277 (issued to Kazunori Iwamoto on Jul. 14, 1998), U.S. Pat. No. 5,526,093 (issued to Kazhiro Takahachi on Jun. 11, 1996), and U.S. Pat. No. 5,842,824 (issued to Kenji Nishi on Dec. 1, 1998).
The wafer alignment process mentioned above generally consists of a wafer pre-alignment step which is carried out on a wafer pre-alignment stage and a main wafer alignment step carried out on a main wafer stage. In the wafer pre-alignment step, the position of a wafer is determined by both an edge sensor which detects the edge of the wafer and by an alignment mark sensor which detects an alignment mark on the wafer.
Once pre-aligned, the wafer is then transferred to the main wafer stage. There, the position of the wafer is accurately detected by a number of minute detecting sensors. The wafer is positioned in final alignment with the mask based on the position detected by the sensors.
FIG. 1
is a schematic-plan view of a conventional light exposure system
500
. As shown in
FIG. 1
, the light exposure system
500
includes a wafer transfer stage
510
for storing a wafer W, a wafer pre-alignient stage
520
for pre-aligning the wafer W transferred by the wafer transfer stage
510
, and a main wafer stage
530
for precisely aligning the wafer W transferred from the wafer pre-alignment stage
520
. The wafer pre-alignment stage
520
is positioned between the wafer transfer stage
510
and the main wafer stage
530
.
The wafer W on the wafer transfer stage
510
is coated with a photoresist. The photoresist coating is performed by a spinner executing a spin-coating method. The wafer W coated with the photoresist is transferred to the wafer transfer stage
510
by a first handler
512
once the coating process is completed.
The wafer pre-alignment stage is provided with second and third handlers
522
and
532
. The second handler
522
functions to transfer the wafer W from the wafer transfer stage
510
to the wafer pre-alignment stage
520
, and to return the wafer W from the wafer pre-alignment stage
520
to its original position on the wafer transfer stage
510
after the wafer W has been subjected to a light exposure process.
The third handler
532
functions to transfer the wafer W from the wafer pre-alignment stage to the main wafer stage
530
, and to return the wafer W at the completion of a light exposure process from the main wafer stage to its original position on the wafer pre-alignment stage
520
. A pivotal movement of the third handler
532
over a range of 120 degrees enables the third handler
532
to return the wafer W to its original position on the wafer pre-alignient stage
520
.
The wafer pre-alignment stage
520
is also provided with an edge sensor
550
and an alignment mark sensor
560
. The edge sensor
550
is used to detect a flat-zone of the wafer W and includes a light emitting device (not shown) and a light receiving device (not shown). Because the alignment mark sensor
560
detects an alignment mark formed on a side portion of the wafer W after the flat-zone has been detected by the edge sensor
550
, a fine and accurate pre-alignment can be achieved in the wafer pre-alignment stage
520
.
The main wafer stage
530
is provided with a number of light detecting sensors
534
which are used to detect the position of the wafer W on the main wafer stage
530
. The detected position is then output to a controller (not shown) which activates a wafer positioning device (not shown) based on the information outputted by the light detecting sensors
534
to finely control the position of the wafer W on the main wafer stage
530
. Due to such fine alignment processes carried out by the wafer pre-alignment and wafer main stages, thin films can be formed on the wafer-W without the occurrence of an overaly. Here, the term overlay refers to a case in which a second thin film is deposited on the surface of a first thin film while being offset from its intended overlying position relative thereto.
After being aligned in the main wafer stage
530
, the wafer W is exposed to UV-rays radiating from a UV-generating device
536
to form a photoresist pattern on the upper surface of the wafer-W. In this exposure process, a mask is interposed between the photoresist and the UV-generating device
536
.
The operation of the conventional light exposure system
500
will now be described in detail.
First, the wafer W coated with a photoresist by the spinner
540
is transferred to the wafer transfer stage
510
by the first handler
512
.
The wafer W awaits awaits processing in the wafer transfer stage
510
. Once its turn arrives, the wafer W is then transferred to the wafer pre-alignment stage
520
by the second handler
522
. The wafer W is placed in the wafer pre-alignment stage
520
in a position between the alignment mark sensor
560
and the edge sensor
550
. Subsequently, the wafer W is rotated at a predetermined speed by a rotating device (not shown) until a flat-zone has been detected by the edge sensor
550
.
Once the flat-zone has been detected, the alignment mark sensor
560
detects an alignment mark formed on the wafer W. During the detection process, the wafer W is rotated in minute angular increments until the alignment mark has been detected. At the completion of the pre-alignment process, the wafer W is then transferred to the main wafer stage
530
by the third handler
532
.
At the main wafer stage
530
, the light detecting sensors
534
detect the position of the wafer W. The light detecting sensors
534
are minute sensing devices which continuously send electric signals, corresponding to the position of the wafer W to the controller. Based on the signals received, the controller activates the wafer positioning device to finely adjust the position of the wafer W to a predetermined position on the main wafer stage
530
.
After the completion of the aligning process in the main wafer stage
530
, the controller sends an electric signal to the UV-generating device
536
commanding the UV-generating device
536
to irradiate the wafer W. In the irradiating process, a mask having a predetermined pattern is interposed between the photoresist and the UV-generating device
536
to cause respective portions of the polymer in the photoresist formed on the upper surface of the wafer W to become soluble and to be left non-soluble.
Then the wafer W is transferred to the wafer pre-alignment stage
520
by the third handler
532
. The wafer W is then returned from the wafer pre-alignment stage
520
to its original position on the wafer transfer stage
510
by the second handler
522
.
Thereafter, the wafer W is transferred to a subsequent stage to be cleaned with a developer for removing the soluble polymer portion of the photoresist and thereby produce the same pattern that was on the mask.
The conventional light exposure apparatus, such as the light exposure apparatus
500
described above, has a significant drawback in that a relatively high temperat

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